The wireless communication technology using the visible light has attracted attention from the academic circles and industrial circles in recent years. In particular, while the lighting equipment using light-emitting elements such as a light emitting diode (LED) and so on is widely used, the feasibility research on using a semiconductor LED to implement the visible light communication covered by the wireless communication network is ongoing. The appropriate approach of combining the visible light communication with a wireless sensor network, a wireless local area network (WLAN) and a power-line communication system is also in the discussion. It has been able to prove that such communication mode will be one of the alternative short-distance and ultra-wideband communication modes in the future.
As the light-emitting components used for the high-speed optical data communication, the influence on the human body or medical apparatus should be considered, and the LED has been regarded as the most powerful candidate light-emitting device at present. Meanwhile, in the optical communication, a data rate is dependent on a response speed of the light-emitting device. Therefore, a light-emitting device with the higher-speed response performance such as a laser diode (LD) or a super luminescent diode (SLD) also attracts much attention.
The basic principle of implementing the visible light communication is that: a certain kind of modulation such as pulse width modulation (PWM), pulse position/frequency modulation (PPM) or pulse amplitude modulation (PAM) is performed on the light emitted by the light-emitting device; the modulated light energy is used as data to be transmitted, and transmitted through a spatial channel and received by a photoelectric detector (a sensor) on the target device; and the photoelectric detector converts the received optical signal into an electrical signal and then demodulates the sent data through the follow-up processing. The target device can be a common portable device attached with such function of transmitting the data through the visible light, such as a mobile phone, a digital camera and a notebook computer and so on. Similar to the constitution of the wireless local area network, the portable terminals constitute the nodes in the network, that is, the visible light communication technology can serve as the local area network technology or the underlying technology applied in an access network.
According to the future application scenarios and characteristics of the visible light, the multiple input multiple output (MIMO) may become the mainstream application mode in various scenarios. Moreover, there will be more and more various portable devices equipped with cameras. It is not difficult to imagine that using various LEDs as an information releasing system and various portable/mobile terminals as a receiving system is a simple and convenient communication mode. At present, there has been no specific method for implementing the visible light communication in the industry.